The broad scope of this investigation is to perform experimental absorption and emission spectroscopy, photochemistry, flash spectroscopy, lifetime data as well as theoretical calculations on model visual pigments. These will provide information on the assignment of the excited states and the lowest excited state, utilization of absorbed quanta, excited states important in photoisomerization and structural aspects of such pigments. Furthermore, in combination, these data should provide insight into the mechanism and nature of intermediates in the rhodopsin bleaching process. The visual pigments that will be included are the isomeric retinals, isomeric n-butylamine Schiff bases of the retinals and protonated derivatives, isomeric retinols and some isomeric retenoic acids. Measurements will include fluorescence and phosphorescence spectra, lifetimes and quantum yields of the latter, flash spectroscopy to determine triplet state occupation, photoisomerization quantum yields, absorption spectra and theoretical calculations. The latter will be used to both interpret experimental results and provide data not amenable to experimental investigation. Experiments will be done in several solvents and at several temperatures. NMR spectroscopy (C-13 and proton) will be done on retinals and on retinal Schiff bases and protonated Schiff bases. The principal goal is to establish structures of these in solution and determine charge densities on the polyene carbon atoms.